The invention concerns a device for determining the density of an electrolyte with at least two immersion tubes submerging with an open tube opening up to different depths into the electrolyte, which can be filled with gas up to an assigned gas depth and which have a gas depth difference with respect to each other, and with at least one pressure sensor for determining the pressure difference in the immersion tubes.
A device of this kind is already known, for example, from the xe2x80x9cHandbook of Industrial Measurement Technologyxe2x80x9d by Prof. Dr. P. Profos and published by Vulkan Publishers of Essen, which appeared in the year 1987. In the article entitled xe2x80x9cHydrostatic Measuring Methods,xe2x80x9d which appeared in the fourth edition on pages 639 to 640, is disclosed a device, wherein an inert gas is injected via two immersion tubes, which are submerged in a liquid at different depths. The gas flow coming out of the deeper-lying tube opening has to overcome a greater hydrostatic pressure of the liquid than the one coming out of the higher-lying tube opening. The differential pressure which exists in the tubes is only dependent upon the density of the liquid. Via a connection of the immersion tubes to the differential pressure manometer can be calculated the density of the liquid. The constant injection of inert gas, however, requires a technically complicated gas pressure supply, which is prone to errors and causes a high energy consumption. Furthermore, the gas pressure supply is bulky because of its individual volume. Another disadvantage consists in that the constant gas generation in the liquid is frequently undesirable with respect to corrosion and the introduction of foreign substances.
German patent publication 3,030,779 discloses a process for measuring the charge state of electric accumulators as well as a device for carrying out the process. The device disclosed therein comprises a vertically arranged pressure-resistant tube, which is filled with gas or liquid, and to which gas bellows are connected at different heights. Between the connection points of the gas bellows is arranged a pressure transducer, which is connected via a measuring line to an external electronic meter. The pressure transducer seals off the tube, so that the meter shows the differential pressure existing at the gas bellows and therefore an average density existing between the gas bellows. The individual volume required by the device, however, is considerable because of the transverse expansion of the gas bellows so that a device of this kind cannot be used, for example, in narrow cramped lead accumulators. Also, because of the individual volume of the gas bellows, inaccuracies occur even with respect to the exact immersion depth of the gas bellows.
The object of the invention is to provide a device of the kind described above, which allows a simple, less error-prone gas filling of the immersion tubes and which has a individual volume which is as small as possible.
This object is attained according to the invention in that electrodes connected to a voltage source are arranged in the interior of the immersion tubes, with which gas can be produced upon contact with the electrolyte to fill the immersion tubes up to the corresponding gas depth.
The electrochemical gas generation simplifies the filling of the immersion tubes and makes superfluous an error-prone mechanic gas pressure generation, so that annoying maintenance work can be eliminated. The arrangement of the electrodes in the interior of the immersion tubes further reduces the device in size and facilitates therefore its use in fields, which are characterized by an effective space utilization.
In a preferred embodiment, the device according to the invention has vertically-directed immersion tubes, wherein the corresponding electrode has an immersion depth which essentially coincides with the gas depth of the corresponding immersion tube.
To connect the electrodes to the electric voltage source are provided advantageous electrode connecting lines, each surrounded by an acid-resistant insulation.
In a practical further development, each electrode connecting line consists of an elastic material and has in the transverse direction a waved wire structure, so that, in a stretched position, pressure forces can be produced on an inner wall of the immersion tube to hold the corresponding electrode.
In a variation thereof, the immersion tube has in its interior an electrode fixation, which is made of an elastic plastic material, and which is connected via radially running transverse struts and a circular section connected to the transverse struts to a passage opening for guiding through the electrode connecting line, wherein the circular section is fixedly connected to the transverse struts and the length of the transverse struts is adapted to the inner diameter of the corresponding immersion tube in such a manner that) in an inserted position of the immersion tube, the holding forces necessary for the fixation can be generated.
In another variation thereof, a mounting headpiece is provided, which can be gas-tight installed on the tube opening, which has a gas outlet opening on its beveled end facing away from the immersion tube as well as a mounting area fixedly connected to the corresponding electrode.
In a preferred embodiment, the immersion tubes have beveled tube ends to simplify the discharge of the escaping gas bubbles.
In a related further development, the immersion tubes have fixed lateral passage openings, wherein in another different exemplary embodiment, a lateral grooving of the immersion tubes is provided.
At the end facing away from the electrolyte, the immersion tubes are advantageously gas-tight connected to a connecting nozzle, which is made of plastic, and which has on its side wall a line entry arranged for a gas-tight passing through of the corresponding electrode connecting line.
In an alternate exemplary embodiment, the device according to the invention has immersion tubes, which are gas-tight connected at their end facing away from the electrolyte to a connecting nozzle, which has at least by sections an electrically conducting side wall, at whose outer and inner sides the corresponding electrode connecting lines are conductively attached.
In a preferred embodiment, the electrodes, which are submerged in an aqueous electrolyte solution, are made of a material with low hydrogen surge and connected to an accumulator electrode of an accumulator, which is negative in its charged condition.
In a different exemplary embodiment, the device according to the invention comprises a DCxe2x80x94DC converter, which is arranged for converting a decreasing DC voltage occurring between two accumulator electrodes into a higher DC voltage and for applying the increased voltage on an electrode, on the one hand, and, on the other hand, on an opposite electrode surrounded by a microperforated sleeve tube.
For an electrochemical hydrogen gas formation, the electrodes are suitably negatively charged with respect to the opposite electrode.
As an alternative thereto, the electrodes can be positively charged with respect to the opposite electrode for the electrochemical formation of oxygen gas.
It is also appropriate to produce the electrodes and their assigned electrode connecting lines as one piece and of the same material, especially lead.
In a variation thereof, the electrode connecting line is made of copper or graphite and is connected to the corresponding electrodes by means of a soldering or welding seam.
If the electrode is made according to the invention of palladium, platinum, or a similar alloy with a merely low hydrogen surge, it is practical that the corresponding electrodes can be configured at their end areas of the corresponding electrode connecting line, wherein the non-coated section of the corresponding electrode connecting line is enclosed by an acid-resistant insulation.
In a modification of this exemplary embodiment, the corresponding electrode is configured as a coating of an end area of the inner wall of the corresponding immersion tube, to which a coating, which acts as an electrode connecting line, is electrically conductively connected.
In another practical further development, the device comprises a temperature sensor, which is submerged in the electrolyte, wherein the temperature sensor and the or each pressure sensor is connected to a data processor for digitalizing the measurement signals, which is connected via a data bus to a microcontroller for calculating the charged condition from the measured acid density of the accumulator.
For an advantageously compact configuration of the device, two immersion tubes have differently dimensioned diameters, wherein the first immersion tube extends at least in part into the interior of the second immersion tube.
In another exemplary embodiment, the device according to the invention has an elastic outer hose, which stretches around the sleeve tube, the temperature sensors, and the temperature measuring line to support the two immersion tubes.
In an exemplary embodiment of the device according to the invention for measuring an acid layer, a desired number of immersion tubes and a number of pressure sensors reduced by one with respect to the number of immersion tubes are provided for measuring the pressure difference between the respective immersion tubes of a immersion tube pair, wherein the immersion tube pairs with their corresponding gas depths assigned to the pressure sensors delimit layers of the electrolyte at different depths, so that the measured data provided by the pressure sensors can be assigned to the layers.